Today, Internet search engines, such as those provided by Yahoo! Inc., help people to find, on the Internet, resources in which those people are interested. A search engine is usually implemented as a computer program that executes on an Internet-accessible server computer. Typically, a search engine provides a user interface via a web browser (e.g., Mozilla Firefox). A user can enter one or more search terms—usually words—into this user interface and instruct the search engine to search for Internet-available resources, such as Hypertext Markup Language (HTML)-encoded web pages, that are relevant to the search terms. The search engine maintains an index that indicates, for each resource that has been previously discovered by a web-crawling component of the search engine, words that are contained in or otherwise pertinent to that resource. The search engine ranks at least a subset of the indexed resources based in part on the occurrences of the submitted search terms in each resource; resources which contain more instances of the search terms tend to be ranked higher than resources which contain fewer instances of those search terms. The search engine generates a search results page that presents references to the most highly ranked results in rank order, and returns this search results page to the user in response to his request.
Sometimes, however, such a ranked list of references to resources isn't the best way to satisfy the user's information need. For example, if the user entered a query such as “most expensive cars,” then many of the most highly ranked resources would probably contain the words “expensive” and “car.” However, if the search results page returned in response to that query merely contains references to the web pages that have the most occurrences of the words “expensive” and “car,” then the user may be disappointed that the results did not make it immediately clear to him what the actual names of the most expensive cars are. The user is likely to be disappointed even if some of those web pages actually do mention the names of some expensive cars, especially if the names of those cars are not apparent in the search results page due to their absence from the abstracts or summaries shown for each reference. The traditional handling of search requests may often fail to provide the actual information in which the user is truly interested (e.g., actual names of expensive cars).
The approaches described in this section are approaches that could be pursued, but not necessarily approaches that have been previously conceived or pursued. Therefore, unless otherwise indicated, it should not be assumed that any of the approaches described in this section qualify as prior art merely by virtue of their inclusion in this section.